Chinese scientists say 2% probability of asteroid hitting Earth

Chinese scientists have been continuously observing an asteroid that may collide with Earth in 2032 since early January, calculating its probability of impact to be around 2 percent.

"As observational data accumulates, the calculations of its orbit will become more accurate, and the probability of it impacting Earth will also change. So the public need not panic and should await further results from astronomers.," said Zhao Haibin, director and researcher of the Department of Planetary Science and Deep Space Exploration at the Purple Mountain Observatory of the Chinese Academy of Sciences.

The asteroid, designated 2024 YR4, has an estimated diameter between 40 and 90 meters, roughly the size of a large building. It was discovered on December 27 by an Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope located in Chile, scientists said.

Previously, NASA's Near-Earth Object monitoring system Sentry calculated the probability of 2024 YR4 impacting Earth at 2.1 percent, while the European Space Agency's (ESA) Near-Earth Object Coordination Centre calculated the probability at 2.02 percent.

"The orbit of an asteroid is primarily calculated through optical observations. Asteroids shine by reflecting sunlight, and observing them with telescopes, along with the surrounding stars in their field of view, helps us determine their coordinates in the celestial sphere. This, in turn, allows us to calculate their orbits," Zhao said.

The orbit of this asteroid has a relatively high eccentricity, meaning its path is elliptical. It passes near Earth's orbit about every four years. The period from the end of last year to the beginning of this year was a good observation window, and there will be another favorable observation window in 2028, he said.

Experts studying asteroids at the CAS indicate that although our current technology makes it difficult to directly intercept an asteroid, but "we can alter its trajectory by a few millimeters per second".

However, there are several ways to prevent such near-Earth asteroids from impacting Earth, such as launching rockets to push it off its original path or evacuating people when it is about to impact, minimizing its effects.

"A planet with a diameter greater than 1,000 kilometers impacting Earth would cause catastrophic damage, and if the diameter is around 10 kilometers, it could lead to species extinction," said a scientist who wished to remain anonymous.

"However, an asteroid with a diameter of a few dozen meters could devastate an area of several thousand square kilometers, equivalent to a large city, if it impacts Earth without any preventive measures," he said.

"Given that we have already discovered an asteroid with a diameter of around 50 meters, we will undoubtedly develop a response plan, meaning the public need not worry excessively," Zhao said.

The International Asteroid Warning Network (IAWN) and the Space Mission Planning Advisory Group (SMPAG) have been operating since 2013, monitoring and issuing warnings for asteroids that pose a potential impact risk.

For asteroids with a diameter greater than 10 meters and an impact probability of more than 1 percent, the IAWN will issue a warning, calling on astronomers worldwide to observe, Zhao said.

"If the asteroid has a diameter greater than 20 meters and a 10 percent probability of impact within the next 20 years, the SMPAG will activate a response mechanism. This involves accurately assessing the impact risk corridor for Earth and preparing civil defense measures such as personnel evacuation," Zhao said.

"If the asteroid's diameter exceeds 50 meters and there is a 1 percent probability of impact within 50 years, active defense plans, such as launching spacecraft to alter its orbit, may be initiated," he added.

At a scientific conference held in Beijing in 2018, Chinese scientists discussed the forefront science and key technologies related to asteroid monitoring and early warning, safety defense, and resource utilization.

"If we need to defend against an asteroid with a diameter of around 50 meters, we might need to start deploying measures 3 to 4 years in advance," the anonymous scientist said.

Chinese scientists have achieved notable progress in the detection and monitoring of near-Earth asteroids. In particular, the Near-Earth Object Telescope at the Purple Mountain Observatory and the Wide Field Survey Telescope, a collaboration between the University of Science and Technology of China and the Purple Mountain Observatory, have delivered significant results in recent years. To date, China has discovered over 60 near-Earth asteroids.

"This also reflects China's active commitment to fulfilling its responsibilities as a major nation in the field of asteroid monitoring, early warning, and defense," said Zhao.